Virtual reality cinema-immersive movie watching for headmounted displays

ABSTRACT

Peripheral-vision expanded images are streamed to a video streaming client. The peripheral-vision expanded images are generated from source images in reference to view directions of the viewer at respective time points. View direction data is collected and received in real time while the viewer is viewing display images derived from the peripheral-vision expanded images. A second peripheral-vision expanded image is generated from a second source image in reference to a second view direction of the viewer at a second time point. The second peripheral-vision expanded image has a focal-vision image portion covering the second view direction of the viewer and a peripheral-vision image portion outside the focal-vision image portion. The second peripheral-vision expanded image is transmitted to the video streaming client.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/753,777, filed Oct. 31, 2018, which is hereby incorporated byreference in its entirety.

TECHNOLOGY

The present invention relates generally to image coding and rendering,and in particular, to image coding related to virtual realitycinema-immersive movie watching for headmounted displays.

BACKGROUND

Regular content viewed on a virtual reality (VR) headset looks dull.Watching a traditional movie in VR presents the viewer with the worst ofboth worlds—lower resolution and lower display quality as compared witha high-end television—with none of the immersive features of VR tocompensate.

Existing solutions for watching traditional content (such as from theNetflix app) in VR are very underwhelming. The content is shown to auser in a flat rectangle—which is only a portion of an overall virtualworld, for example depicted with the user's headmounted display. Theuser is left watching a low-quality version of the original in the flatrectangle amid the overall virtual world presented to the users.

The approaches described in this section are approaches that could bepursued, but not necessarily approaches that have been previouslyconceived or pursued. Therefore, unless otherwise indicated, it shouldnot be assumed that any of the approaches described in this sectionqualify as prior art merely by virtue of their inclusion in thissection. Similarly, issues identified with respect to one or moreapproaches should not assume to have been recognized in any prior art onthe basis of this section, unless otherwise indicated.

BRIEF DESCRIPTION OF DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings and in whichlike reference numerals refer to similar elements and in which:

FIG. 1 illustrates an example representation of a vision field of anaverage viewer's eye;

FIG. 2A illustrates example image depth data generated from atwo-dimensional image; FIG. 2B illustrates example curved imagegenerated from a flat image; FIG. 2C illustrates an example audiorendering environment in which sound source rendering can be retargetedfor peripheral-vision expanded video content; FIG. 2D illustrates anexample peripheral-vision expanded image;

FIG. 3A through FIG. 3C illustrate example video streaming servers andclients;

FIG. 4A and FIG. 4B illustrate example process flows; and

FIG. 5 illustrates an example hardware platform on which a computer or acomputing device as described herein may be implemented.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments, which relate to virtual reality cinema-immersivemovie watching for headmounted displays, are described herein. In thefollowing description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be apparent, however,that the present invention may be practiced without these specificdetails. In other instances, well-known structures and devices are notdescribed in exhaustive detail, in order to avoid unnecessarilyoccluding, obscuring, or obfuscating the present invention.

Example embodiments are described herein according to the followingoutline:

-   -   1. GENERAL OVERVIEW    -   2. THE HUMAN VISION FIELD    -   3. VIEW DIRECTION TRACKING    -   4. PERIPHERAL-VISION EXPANDED IMAGES    -   5. EXAMPLE VIDEO STREAMING SERVERS AND CLIENTS    -   6. EXAMPLE PROCESS FLOWS    -   7. IMPLEMENTATION MECHANISMS—HARDWARE OVERVIEW    -   8. EQUIVALENTS, EXTENSIONS, ALTERNATIVES AND MISCELLANEOUS

1. General Overview

This overview presents a basic description of some aspects of an exampleembodiment of the present invention. It should be noted that thisoverview is not an extensive or exhaustive summary of aspects of theexample embodiment. Moreover, it should be noted that this overview isnot intended to be understood as identifying any particularlysignificant aspects or elements of the example embodiment, nor asdelineating any scope of the example embodiment in particular, nor theinvention in general. This overview merely presents some concepts thatrelate to the example embodiment in a condensed and simplified format,and should be understood as merely a conceptual prelude to a moredetailed description of example embodiments that follows below. Notethat, although separate embodiments are discussed herein, anycombination of embodiments and/or partial embodiments discussed hereinmay be combined to form further embodiments.

Techniques as described herein can be implemented in various videoapplications to remap source images of limited fields of vision to(foveal-vision dependent) peripheral-vision expanded images. Each of theperipheral-vision-expanded images is generated from a correspondingsource image in the source images of limited fields of vision based on aviewer's view direction determined or predicted for a corresponding timepoint. Each of the peripheral-vision-expanded images comprises afoveal-vision image portion that preserves or closely approximatesspatial relationships as depicted in a corresponding source image andone or more peripheral-vision image portions that do not preserve butrather are spatially stretched to cover the viewer's entire orsubstantially entire peripheral vision field, for example as depicted inthe viewer's headmounted display, (e.g., significantly, etc.) beyondwhat the corresponding source image could cover the viewer's peripheralvision field.

As used herein, the term “preserve” or “closely approximate” may meanthat a foveal-vision image portion (e.g., 2 to 4-degree radius aroundthe viewer's view direction, etc.) in a peripheral-vision-expanded imagehas depicted objects or image details with spatial relationships,geometries, distances, shapes, etc., comparable to those with whichcorresponding depicted objects or image details in a corresponding imageportion in a corresponding source image used to derive theperipheral-vision-expanded image are depicted in the correspondingsource image.

A video application as described herein may refer to any of: videodisplay applications, VR applications, AR applications, automobileentertainment applications, remote presence applications, displayapplications, gaming applications, mobile applications (or mobile apps),internet-based video streaming applications (e.g., Netflix app, etc.),etc.

The techniques can be applied to virtual reality cinema-immersive moviewatching (e.g., for headmounted displays, etc.) for streaming video databetween video streaming server(s) and video streaming client(s). Examplevideo content may include, but are not necessarily limited to, any of:audiovisual programs, movies, video programs, TV broadcasts, computergames, augmented reality (AR) content, virtual reality (VR) content,automobile entertainment content, etc. Example video streaming clientsmay include, but are not necessarily limited to, any of: displaydevices, a computing device with a near-eye display, a head-mounteddisplay (HMD), a mobile device, a wearable display device, a set-top boxwith a display such as television, a video monitor, etc.

As used herein, a “video streaming server” may refer to one or moreupstream devices that prepare and stream video content to one or morevideo streaming clients in order to render at least a portion (e.g.,corresponding to a user's FOV or viewport, etc.) of the video content onone or more (target) displays. The displays on which the video contentis rendered may be part of the one or more video streaming clients ormay be operating in conjunction with the one or more video streamingclients. Example video streaming servers may include, but are notnecessarily limited to, any of: cloud-based video streaming serverslocated remotely from video streaming client(s), local video streamingservers connected with video streaming client(s) over local wired orwireless networks, VR devices, AR devices, automobile entertainmentdevices, digital media devices, digital media receivers, set-top boxes,gaming machines (e.g., an Xbox), general purpose personal computers,tablets, dedicated digital media receivers such as the Apple TV or theRoku box, etc.

Peripheral-vision-expanded video content as described herein can betransmitted to, and used by, a recipient device for rendering thatsupports cinema-immersive video watching experience with correct spatialrelationships of depicted objects and/or image details wherever the(human) viewer directs view directions. The viewer's view directions canbe tracked by any combination of view direction tracking methodsincluding but not limited to gaze tracking, viewport tracking, FOVtracking, viewer position tracking, face tracking, or any other viewdirection tracking methods.

View direction data to track the viewer's view directions is collectedwhile the viewer is viewing the peripheral-vision-expanded images or aderivative version thereof (e.g., display images generated from theperipheral-vision-expanded images by a video rendering device or a videodecoder operating in conjunction with the video rendering device, etc.).Example view direction data may include, without limitation, lineardisplacements, angular displacements, linear motions or translations,angular motions or rotations, pitch, roll, yaw, sway, heave, surge, upto six degrees of freedom, etc., that may be collected by anycombination of gaze tracking devices, position tracking devices,viewport tracking devices, face tracking devices, FOV tracking devices,etc. The viewer's view directions at a plurality of time points may bedetermined. The viewer's view directions can be (e.g., additionally,optionally, alternatively, etc.) used on the recipient device itself togenerate new views by implementing some or all techniques as describedherein on the recipient device (or a device operating in conjunctionwith the recipient device) until the upstream devices respond with newdata. The viewer's view directions can also be fed back to upstreamdevices (or a device operating in conjunction with the upstream device)to generate, from the source images, specific peripheral-vision-expandedimages in reference to the viewer's view directions.

As used herein, a peripheral-vision-expanded image refers to an image inwhich only a region or image portion covering the viewer's vision field(e.g., sufficiently covering the viewer's foveal-vision, covering 100%,50%, 20%, 10%, 5%, etc., more than the viewer's foveal-vision, etc.) isgiven image data of depicted objects and/or image details that preserveor closely approximate original spatial relationships, originalgeometries, original distances, original shapes, etc., as depicted in acorresponding source image, while image data covering other regions ofthe viewer's vision field can be (e.g., greatly, etc.) stretched andeven distorted (e.g., through reverse fisheye mapping, conformalmapping, etc.) with peripheral-vision depicted objects and/or imagedetails that do not preserve original spatial relationships, originalgeometries, original distances, original shapes, etc., as depicted in acorresponding source image.

Instead of sending (e.g., relatively uniform, etc.) high-quality imageswith large data volumes throughout the viewer's viewport of the viewer'simage display, the specific peripheral-vision-expanded images generatedin reference to the viewer's view directions can comprise much less datavolumes by sending relatively low image qualities in the viewer'speripheral vision fields as depicted in the viewer's viewport of theviewer's image display.

For example, to reduce bandwidth usages, dynamic ranges in (e.g.,specific to, etc.) peripheral-vision image portions may be (spatiallyvariably) clipped or greatly compressed in a peripheral-vision-expandedimage. Dynamic ranges may be the greatest in the viewer's foveal visionand (e.g., gradually) reduced from near-foveal vision to far peripheralvision in the viewer's vision field.

Additionally, optionally or alternatively, spatial resolutions may be(spatially variably) reduced in the peripheral-vision-expanded image.Spatial resolutions may be the greatest in the viewer's foveal visionand (e.g., gradually) reduced from near-foveal vision to far peripheralvision in the viewer's vision field.

Additionally, optionally or alternatively, color accuracies/precisionsmay be (spatially variably) reduced in the peripheral-vision-expandedimage. Color accuracies/precisions may be the greatest in the viewer'sfoveal vision and (e.g., gradually) reduced from near-foveal vision tofar peripheral vision in the viewer's vision field.

Additionally, optionally or alternatively, faithful or high-fidelityrepresentations of depicted objects, image details, spatial relationsthereof, etc., may be (spatially variably) reduced in theperipheral-vision-expanded image. Faithful or high-fidelityrepresentations of depicted objects, image details, spatial relationsthereof, etc., may be the greatest in the viewer's foveal vision and(e.g., gradually) reduced from near-foveal vision to far peripheralvision in the viewer's vision field.

Instantaneous flashes, pulsating or abrupt changes in light levels ofthe viewer's peripheral vision may be dampened or smoothened in somecircumstances. Stretching operations in the viewer's peripheral visionmay implement a smoothening process to allow spatial distortionsintroduced by the stretching operations in the viewer's peripheralvision to smoothly transition (e.g., relatively slowly go up, relativelyslowly go down, etc.) from near foveal vision spatial regions of aperipheral-vision-expanded image to far peripheral vision spatialregions of the same peripheral-vision-expanded image.

Techniques as described herein can be used to allow a user of adownstream recipient device to freely vary the user's viewing angles orfields of view to display or rendered images generated fromperipheral-vision-expanded images as described herein from a videostreaming server. In most if not all operating scenarios, the user canbe presented with focal-vision video content with the most faithful orthe highest fidelity depicted objects and/or image details for aseamless viewing experience that is relatively free from visualartifacts, physiological discomforts, etc., associated with some otherapproaches that do not adopt the techniques as described herein. Thevisual artifacts, physiological discomforts, etc., associated with theother approaches may include, but are not necessarily limited to, anyof: motion artifacts such as unable to maintain smooth pursuit,prolonged lags in transitioning to fine image details as perceived bythe human vision, coarse image details noticeable within a focal viewingarea of the human vision, mismatches between a user's naturalvision-related intuition and video content as actually rendered to theuser, sudden drop of levels of image details when a viewer moves viewingangles, perceptible slow transitioning from coarse image details to fineimage details, showing fuzzy images for previously occluded imagedetails when a viewer moves viewing angles, etc.

Spatially differentiated image metadata portions may be generated fordifferent image portions for a source image as described herein. Arecipient video decoding device that receives the source image and theimage metadata portions can use the image metadata portions to performrespective stretching operations (including but not limited to attendantimage processing operations and/or other image processing operations) onthe image portions of the source image to generate a correspondingperipheral-vision-expanded image and/or a corresponding display image tobe rendered on one or more target displays operating in conjunction withthe recipient video decoding device. Example target displays mayinclude, without limitation, headmounted displays, AR displays, VRdisplays, omni-vision displays, 360 degree displays, home theaterdisplays, CAVE-type displays, etc.

In some example embodiments, mechanisms as described herein form a partof a media processing system, including but not limited to any of:cloud-based server, mobile device, virtual reality system, augmentedreality system, headmounted devices, headmounted displays, head updisplay device, helmet mounted display device, CAVE-type system,wall-sized display, video game device, display device, media player,media server, media production system, camera systems, home-basedsystems, communication devices, video processing system, video codecsystem, studio system, streaming server, cloud-based content servicesystem, a handheld device, game machine, television, cinema display,laptop computer, netbook computer, tablet computer, cellularradiotelephone, electronic book reader, point of sale terminal, desktopcomputer, computer workstation, computer server, computer kiosk, orvarious other kinds of terminals and media processing units.

Various modifications to the embodiments and the generic principles andfeatures described herein will be readily apparent to those skilled inthe art. Thus, the disclosure is not intended to be limited to theembodiments shown, but is to be accorded the widest scope consistentwith the principles and features described herein.

2. The Human Vision Field

Techniques as described herein can be implemented based on the knowledgeof the (human) eye and how the eye perceives luminance, colors, spatialresolution, etc. These techniques may be applied based on the individualviewer's specific vision characteristics or a user population's averageor collective vision characteristics.

FIG. 1 illustrates an example representation of a vision field of anaverage viewer's eye. Cone and rod distributions (in the eye) can besegmented into different distribution ranges of cones and rods andfurther projected into an angular vision field representation (of theeye) as illustrated in FIG. 1. Highest levels of visual perception areachieved in the eye's foveal (vision field) region 102.

By way of example but not limitation, the widest angular range in theeye's vision field is along the horizontal direction of FIG. 1, which isparallel to the inter-pupil line between the viewer's two eyes, withoutconsidering visual constraints from facial anatomy, and may beapproximately 180 angular degrees.

Each of concentric circles (e.g., labelled as 30°, 60°, 90°, etc.)represents directions of equal (or the same) angular degree relative toa view direction of the viewer's left or right eye. It should be notedthat angles such as 30°, 60°, 90°, etc., are for illustration purposesonly. Different values of angles or different set of angles can be usedto define or describe a viewer's vision field. The view direction (notshown in FIG. 1) is pointed vertically out of the plane of FIG. 1 at theintersection of a transverse direction 112 and a vertical direction 114in a foveal region 102 (the darkest fill pattern). Here, the transversedirection (112) and the vertical direction (114) form a plane verticalto the view direction.

As illustrated in FIG. 1, the vision field of the eye may be partitioned(e.g., logically, projected by certain partitions in the distributionsof densities of rods/cones, etc.) into the foveal region (102)immediately surrounded by a paracentral region 104. In some embodiments,the foveal region (102) may correspond to the viewer's fovea vision andextend from zero (0) angular degree to a first angle (e.g., 2-4 angulardegree, 3-7 angular degrees, 5-9 angular degrees, etc.) relative to theview direction. In some embodiments, the paracentral region (104) mayextend from the first angle to a second angle (e.g., 6-12 angulardegrees, etc.) relative to the view direction.

The paracentral region (104) is immediately surrounded by anear-peripheral region 106. The near-peripheral region (106) isimmediately adjacent to the mid-peripheral region (108), which in turnis immediately adjacent to the rest of the vision field, afar-peripheral region 110. In some embodiments, the near-peripheralregion (106) may extend from the second angle to a third angle (e.g.,25-35 angular degrees, etc.) relative to the view direction. In someembodiments, the mid-peripheral region (108) may extend from the thirdangle to a fourth angle (e.g., 50-65 angular degrees, etc.) relative tothe view direction. The far-peripheral region (110) may extend from thefourth angle to the edge of the vision field.

The first, second, third and fourth angles used in this example logicalpartition of the vision field may be defined or specified along thetransverse direction (112). When the vision field of FIG. 1 correspondsto that at a front level viewing direction, the transverse direction(112) may be the same as, or parallel to, the viewer's interpupil line.

It should be noted that different schemes of logically partitioning aviewer's vision field may be used in addition to, or in place of, thescheme of logically partitioning the viewer's vision field into foveal,paracentral, near-peripheral, mid-peripheral, far-peripheral, etc.,regions based on angles as illustrated in FIG. 1.

For example, in some embodiments, the viewer's vision field may bepartitioned into more or fewer regions such as a combination of a fovealregion, a near-peripheral region and a far-peripheral region, etc.,without a paracentral region and/or a mid-peripheral region. A spatiallyfaithful representation (or high-fidelity) image portion may be used tocover from the foveal region up to some or all of the near-peripheralregion in such logical partition of the viewer's vision field.

In some embodiments, the viewer's vision field may be partitioned basedon other quantities other than angles as illustrated in FIG. 1. Forexample, in a non-limiting implementation, the foveal region may bedefined as a vision field region that corresponds a viewer'sfoveal-vision. The paracentral region may be defined as a vision fieldregion that corresponds a viewer's retina area where cone/rod densitiesexceed relatively high cone/rod density thresholds. The near-peripheralregion may be defined as a vision field region that corresponds aviewer's retina area where cone/rod densities does not exceed relativelyhigh cone/rod density thresholds respectively but does exceedintermediate cone/rod density thresholds. The mid-peripheral region maybe defined as a vision field region that corresponds a viewer's retinaarea where cone/rod densities does not exceed intermediate cone/roddensity thresholds respectively but does exceed relatively low cone/roddensity thresholds. A focal-vision region as described herein may coverfrom the viewer's foveal-vision up to some or all of a region (e.g.,some or all of the viewer's near-peripheral vision, etc.) based onthreshold(s) (e.g., cone/rod density threshold(s), etc.) that are notnecessarily angle-based.

Additionally, optionally or alternatively, a combination of two or moredifferent schemes of logically partitioning the viewer's vision fieldand/or other human vision factors may be used to determine afocal-vision region of the viewer's vision field. For example, insteadof using a focal-vision region as described herein to cover the sameangular value range in different angular directions, the focal-visionregion as described herein may cover a larger angular value range alongthe transverse direction (112) than an angular value range covered bythe focal-vision region along the vertical direction (114), as the humanvision system may be more sensitive to image details along thetransverse direction (112) than those along the vertical direction(114).

In some embodiments, a focal-vision region as described herein coverssome or all of: a foveal region (e.g., plus a safety margin, etc.), aparacentral region (e.g., excluding and extending from the fovealregion, etc.), a near-peripheral region (e.g., further excluding andextending from the paracentral region, etc.), a mid-peripheral region(e.g., further excluding and extending from the near peripheral region,etc.), etc.

In some embodiments, a focal-vision region as described herein covers asymmetric angular range representing a symmetric (to the viewer's viewdirection) region of the wide angular range. Examples of thefocal-vision region may include, but are not necessarily limited to, oneof: +/−15 angular degrees, +/−20 angular degrees, +/−25 angular degrees,etc., relative to the viewer's view direction.

In some embodiments, a focal-vision region as described herein covers anasymmetric angular range representing an asymmetric (to the viewer'sview direction) region of the wide angular range. An asymmetric angularrange in a vision field of one eye may be defined or specified ascovering from an interior angle (looking towards the other/conjugateeye) to an exterior angle (looking away from the other/conjugate eye).

In some implementation examples, the asymmetric angular range is biasedwith a preference towards interior directions overlapped in both visionfields of the viewer's left and right eyes. Examples of the interiorangle of the asymmetric angular range with bias to interior angles mayinclude, but are not necessarily limited to, one of: 15 angular degrees,30 angular degrees, 45 angular degrees, etc., relative to the viewer'sview direction. Examples of the exterior angle of the asymmetric angularrange with bias to interior angles may include, but are not necessarilylimited to, one of: 10 angular degrees, 15 angular degrees, 20 angulardegrees, etc., relative to the viewer's view direction.

In some implementation examples, the asymmetric angular range is biasedwith a preference towards exterior directions which may or may not beoverlapped in both vision fields of the viewer's left and right eyes.Examples of the exterior angle of the asymmetric angular range with biasto exterior directions may include, but are not necessarily limited to,one of: 15 angular degrees, 30 angular degrees, 45 angular degrees,etc., relative to the viewer's view direction. Examples of the interiorangle of the asymmetric angular range with bias to exterior directionsmay include, but are not necessarily limited to, one of: 10 angulardegrees, 15 angular degrees, 20 angular degrees, etc., relative to theviewer's view direction.

Additionally, optionally or alternatively, in some embodiments, a visionfield of an eye as described herein takes into considerationvision-related factors such as eye swiveling, viewing constraints fromnose, corneal, eyelid, etc.

Examples of a focal-vision region as described herein may include, butare not necessarily limited to, any combination of one or more of:circular shapes, oblong shapes, oval shapes, heart shapes, star shapes,round shapes, square shapes, polygonal shapes, etc.

3. View Direction Tracking

In some embodiments, only a (e.g., relatively small, etc.) focal-visionregion of the eye's vision field needs to be provided with pixel valueswith the highest dynamic range, the widest color gamut, the highest (orsharpest) spatial resolution, etc. In some embodiments, the focal-visionregion of the eye's vision field may correspond to (e.g., exactly,approximately, no less than 95% of, no more than 105% of, etc.) theentirety of the foveal-vision of the eye up to some or all ofnear-peripheral vision of the eye. In some embodiments, the focal-visionregion of the eye's vision field may additionally include a safetyvision field region.

In some embodiments, the size and/or shape of the safety vision fieldregion in the focal-vision region can be preconfigured to a fixed size(e.g., 0%, 5%, 10%, −5%, −10%, etc.) that does not vary with networkbandwidth, image content, types of computing devices (e.g., helmetmounted display devices, small form factor computing devices such ascredit card size plugin devices, wall displays, etc.) involved in videoapplications, types of rendering environments (e.g., cloud-based videostreaming servers, video streaming servers collocated with videostreaming clients, video streaming servers connected with videostreaming clients over local wireless connections, etc.) involved invideo applications, etc.

In some other embodiments, the size and/or shape of the safety visionfield region in the focal-vision region can be dynamically reconfiguredat runtime, and can vary in a range (e.g., from −10% to 10%, from −5% to5%, from 0% to 5-10%, etc.) with one or more of: network bandwidth,image content, types of computing devices (e.g., helmet mounted displaydevices, small form factor computing devices such as credit card sizeplugin devices, wall displays, etc.) involved in video applications,types of rendering environments (e.g., cloud-based video streamingservers, video streaming servers collocated with video streamingclients, video streaming servers connected with video streaming clientsover local wireless connections, etc.) involved in video applications,etc.

For example, in response to determining that network connections do notsupport a relatively high bandwidth, the size and/or shape of the safetyvision field region may be dynamically shrunk at runtime from 10% to 5%over the eye's foveal-vision. On the other hand, in response todetermining that network connections supports a relatively highbandwidth, the size and/or shape of the safety vision field region maybe dynamically expanded at runtime from 5% to 10% over the eye'sfoveal-vision.

The size and/or shape of the safety vision field region may also be setin dependence on latency in eye tracking. Additionally, optionally oralternatively, eye tracking data as described herein can be used topredict where the viewer would look next and reduce the bandwidth/safetyregion based on the prediction. For example, the user's view directionat runtime may be tracked by a view direction tracking device. The viewdirection tracking device may operate in real time with a display onwhich a sequence of display mapped images is rendered. As the userchanges view directions and/or viewing distances from time to time, theview direction tracking device tracks and computes the viewing anglesand/or viewing distances in a coordinate system in which the sequence ofdisplay mapped images is being rendered, generates a time sequence ofview directions, and signals each view direction in the time sequence ofview directions to a video streaming server as described herein. Eachsuch signaled view direction of the viewer as received by the videostreaming server may be indexed by a time point value. The time pointvalue may be associated or correlated by a video streaming server asdescribed herein with a specific peripheral-vision expanded image in asequence of peripheral-vision expanded images that are used by a videodecoder to generate the sequence of display mapped images.

View direction data may be collected, analyzed and/or shared/transmittedamong view direction tracking devices and streaming devices withrelatively low latency (e.g., within a fraction of one image frame time,within 5 milliseconds, etc.). In an example implementation, the viewdirection tracking data may be shared among these devices using thelowest latency data/network connections where multiple data/networkconnections are available.

In response to determining the viewer's view direction relativelyexpeditiously with relatively low latency (e.g., within a fraction of animage frame time, etc.) based on the view direction data, a videostreaming server (e.g., implemented with one or more upstream devices,etc.) may dynamically shrink the size and/or shape of the safety visionfield region at runtime from 10% to 5% over the eye's foveal-vision. Arelatively small area (e.g., within 20 angular degrees from the viewdirection, etc.) of the highest dynamic range, the widest color gamut,the highest spatial resolution, etc., may be sent in the video signal tothe downstream recipient device.

On the other hand, in response to determining the viewer's viewdirection relatively slowly with relatively high latency (e.g.,exceeding a time threshold, more than the fraction of one image frametime, longer than 5 milliseconds, etc.) based on the view directiondata, the video streaming server may dynamically expand the size and/orshape of the safety vision field region at runtime from 1% to 3%, 2% to6%, 5% to 10%, etc., over the eye's foveal-vision. A relatively largearea (e.g., up to 30 angular degrees from the view direction, etc.) ofthe highest dynamic range, the widest color gamut, the highest spatialresolution, etc., may be sent in the video signal to the downstreamrecipient device. That way, the recipient device of the video signal canhave sufficient image data over a relatively large focal-vision regionto make local decisions based on the view directions for image renderingpurposes.

HDR source images as described herein can be captured/generated with oneor more camera systems deployed in one or more spatial environments.Example spatial environments may include, but are not limited to only,any of: physical spatial environment, simulated spatial environment,movie studios, outdoor scenes, indoor scenes, tunnels, streets,vehicles, ships, aircrafts, outer space, etc. Example camera systems mayinclude, but are not limited to only, any of: light field cameras,multiple cameras with overlapping and/or non-overlapping fields ofvision, digital cameras, analog cameras, webcams, virtual cameras ingame rendering engines, etc.

As used herein, an HDR source image may represent one individual HDRsource image image in a sequence of HDR source images. A video streamingserver may be configured to receive and use the received sequence of HDRsource images as input to prepare peripheral-vision expanded videocontent for streaming to (downstream) video streaming clients in supportof one or more of: video display applications, VR applications, ARapplications, automobile entertainment applications, remote presenceapplications, display applications, etc.

An image (e.g., a source image, a peripheral-vision expanded image, adisplay mapped image, etc.) as described herein can be represented inany of a wide variety of coordinate systems such as a World coordinatesystem, a coordinate system stationary to a camera system, a coordinatesystem fixed relative to a spatial environment, etc. A spatial positionin the image may be either an absolute position (e.g., represented inthe World coordinate system, etc.) or a relative position (e.g.,represented in a relative coordinate system stationary to the camerasystem, etc.).

In some embodiments, a spatial position (e.g., a pixel, etc.) in theimage can be represented by a set of specific (x, y) coordinate values.By way of example but not limitation, the x coordinate value of thespecific (x, y) coordinate values may correspond to a specificlongitudinal degree (ranging from 0 to 360 angular degrees) in the imagerepresentation in a 3D space, whereas the y coordinate value of the (x,y) coordinate values may correspond to a specific latitudinal degree(ranging from 0 to 180 angular degrees) in the image representation inthe 3D space. In various embodiments, geometric transformations can beused to transform a set of (e.g., x, y) coordinate values of a spatialposition in one image representation into another set of (e.g., pitch,roll, yaw, sway, heave, surge, etc.) coordinate values of the sameposition in other image representations, etc.

4. Peripheral-Vision Expanded Images

In some embodiments, an image processing device (e.g., aperipheral-vision expanded image generator 312 of FIG. 3A or FIG. 3C, acomputing device operating in conjunction with the peripheral-visionexpanded image generator (312), etc.) under techniques as describedherein adapts content (including but not limited to traditional content)such as objects and/or image details depicted in source images topresent the adapted content in a manner especially suited to VRpresentation, AR presentation, etc., thereby creating cinema-immersiveexperiences for viewers.

The image processing device may comprise a number of system componentssuch as subsystems or devices each of which may be implemented at leastin part through hardware (e.g., computer processors, non-transitorymedia, digital signal processors, ASICs, FPGAs, ICs, SoC, etc.). Examplesystem components may include, but are not necessarily limited to only,any of: system components implementing automatic or semi-automatic2D-to-3D conversion method/algorithm/process/procedure, etc.

In many operational scenarios, viewing display (or rendered) images witha video application such as a VR application, an AR application, anomnidirectional video application, etc., represents a stereoscopic (ormulti-view) experience.

For example, in operational scenarios in which 3D versions of films areavailable, display (or rendered) images derived from the films can berendered and viewed in stereo 3D.

However, in operational scenarios in which 3D versions of films are notavailable, an automatic or semi-automatic 2D-to-3D conversionmethod/algorithm/process/procedure implemented by the image processingdevice can be employed to obtain a 3D version of adapted imagesgenerated by adapting a 2D version of source images in the films.

FIG. 2A illustrates example image depth data (or image depth map) 226generated from a two-dimensional (2D) image 224, for example in a 2Dversion of a film or a media program. The 2D-to-3D conversionmethod/algorithm/process/procedure of the image processing device mayimplement depth map extraction, image warping, etc., to generate theimage depth data (226).

As illustrated in FIG. 2A, the depth data (226) may comprise one or moredepth data portions for one or more depicted objects and/or imagedetails in the 2D image (224).

For example, a first depth data portion in the depth data (226), asgenerated by the 2D-to-3D conversion method/algorithm/process/procedure,may identify a first depicted object or image detail (e.g., a humanfigure, etc.) as located at a first depth (e.g., coplanar with azero-parallax plane, etc.) from a viewer 222 along a view direction(e.g., a frontal view direction of the viewer's headmounted device 230(e.g., with a headmounted display, etc.), an eye gaze direction of theviewer 222, etc.).

A second depth data portion in the depth data (226), as generated by the2D-to-3D conversion method/algorithm/process/procedure, may identify asecond depicted object or image detail (e.g., a plant, etc.) as locatedat a second depth (e.g., a specific distance in front of thezero-parallax plane, etc.) from the viewer (222) along the viewdirection.

A third depth data portion in the depth data (226), as generated by the2D-to-3D conversion method/algorithm/process/procedure, may identify athird depicted object or image detail (e.g., a wagon, etc.) as locatedat a third depth (e.g., a specific distance behind the zero-parallaxplane, etc.) from the viewer (222) along the view direction.

Additionally, optionally or alternatively, some or all of the depth data(226) may be rectified based at least in part on individual inter-pupildistance (IPD) information and personalized for the viewer (222).Example individual IPD information may indicate whether the viewer hasan average IPD, a smaller IPD, a larger IPD, etc., as compared with aviewer population.

In many operational scenarios, video presentation in a video applicationsuch as a VR application, an AR application, etc., is done as a “flat”virtual screen in the virtual world depicted in the video application.

In operational scenarios in which curved versions of source images arenot available, an automatic or semi-automatic flat-to-curved imageconversion method, algorithm, process, procedure, tool, etc.,implemented by the image processing device can be employed to obtain acurved version of adapted images generated by adapting the flat-imageversion of the source images.

FIG. 2B illustrates example curved image 232 generated from a flat image(e.g., the 2D image (224) of FIG. 2A, etc.), for example in the flatimage version of the source images. In some embodiments, the generatedcurved image (232) may cover the entire (or substantially entire) fieldof view (e.g., 120-degree field of view, 240-degree field of view,360-degree field of view, etc.) as supported by the viewer's headmounteddevice (230).

Curved images (e.g., 232, etc.) generated under techniques as describedherein may be displayed/rendered to result in a cinema-immersiveexperience—which may, but is not limited to, be delivered by way of theviewer's headmounted device (230)—similar to that with a physical curveddisplay such as a Dolby cinema display, an IMAX display, a high-end hometheater display, a television/gaming display, and so forth. Curvedimages, or images adapted to a curved (e.g., virtual, real, etc.) screenor image display support a relatively high-quality viewing experience byminimizing distortion for the viewer as if the viewer is (e.g., always,etc.) guaranteed to be seated at a relatively ideal viewing location inrelation to the virtual or real screen or image display.

A headmounted device such as a VR headset, etc., may encompass a largefield of view of a viewer, significantly more than that in a traditionalhome theater experience. Techniques as described herein can implementimage rendering/presentation methods for presenting images to the viewerin a manner that mimics a home theater experience. These images can bepresented in an immersive setting that encompasses nearly all of theviewer's field of view, as supported by the viewer's headmounted device,to enhance cinema level immersion within the virtual world as depictedthrough the viewer's headmounted device.

In some operational scenarios, some depicted objects and/or imagedetails, such as relatively significant or important elements (e.g.,depicted objects, image details, etc.) of a depicted scene, may beplaced on the periphery of the viewer's vision field (or visible zones),or even outside the viewer's vision field, depending on the viewer'shead position.

The image processing device, or a device operating in conjunctiontherewith, may perform image stretching operations to non-linearlydistort one or more image portions of a source image to generate acorresponding peripheral-vision expanded image in such a way that visionfield areas central to the viewer's attention (e.g., the viewer's fovealvision, the viewer's focal vision, etc.) are not affected, butperipheral zones in the viewer's vision field are stretched to covermore areas than what are supported by the source image. A result is thatthe viewer's peripheral vision field portions as supported by theviewer's headmounted device (230) are covered with image content,thereby generating an immersive feeling. The non-linear distortion canbe attributed to the non-linear cone/rod distribution of the viewer'seye or vision field. As such when travelling away from the fovealregion, the acuity/HDR/Color/pixel depth of an image can be slowlydistorted or varied based on different locations of images thatcorrespond to different regions of near/mid/far peripheral visions.

While image content in the peripheral-vision expanded image is distortedto some extent, for example in the viewer's peripheral vision fieldportions, distortions may not be noticeable since the distortions arelocated on the periphery of the viewer's vision where the human visualsystem may not be able to distinguish in detail.

In response to determining that the viewer's gaze and/or view positionshift to a zone that was previously in the periphery, the imageprocessing device may generate new peripheral-vision expanded imagesthat display newly focused areas undistorted, while distorting zonesthat are now located in the periphery of the viewer's vision, therebymaintaining and continuing to support a cinema-immersive experience.

Image stretching operations as described herein may implement any in avariety of image distortion/expansion methods, algorithms, procedures,tools, and so forth. Example image distortion/expansion operations may,but are not necessarily limited to only, include one or more of: imagedistortion/expansion based on reversed fish-eye lens correction, imagedistortion/expansion using a horizontal plane (e.g., only, etc.), imagedistortion/expansion using projective techniques, imagedistortion/expansion based on geometrical mappings such as conformalmappings, etc.

The viewer's gaze or view direction can be tracked through a gazetracking device operating within or in conjunction with the viewer'sheadmounted device (230).

Techniques as described herein can be implemented to computationallyretarget and enhance (e.g., existing, newly generated, etc.) videocontent by a carefully selected gaze-guided (e.g., projective, etc.)distortion to generate a larger, curved field of view to cover arelatively large field of view up to omnidirectional field of view.Depicted objects and/or image details in resultant peripheral-visionexpanded images may be segmented in spatial depths by way of 2D to 3Dconversion. Additionally, optionally or alternatively, depth informationas described herein can be used to determine or detect whether objectsin a peripheral region of an image has depth data indicating that thoseobjects are far off. If that is the case, then the amount ofdeterioration in acuity/HDR/Color/pixel depth in that peripheral regionof the image may be increased. Thus, distortion may be added or reducedbased on depth information. The depth information may be used forsegmenting images and then compressing the segmented images. The depthinformation also may be used for classifying regions of images and thendistorting some of the regions of the images.

In some embodiments, as illustrated in FIG. 2C, based on new positionsof the depicted objects and image details in the peripheral-visionexpanded images and head tracking of the viewer, sound sources in one ormore scenes as represented in the peripheral-vision expanded images canbe retargeted to match the viewer's view of the scenes and spatialrelationships between the viewer's position and view direction and new(or retargeted) sound source positions as represented in theperipheral-vision expanded images.

In some embodiments, an audio rendering system may operate within theviewer's headmounted device (e.g., implementing binaural renderingtechniques, etc.) or in conjunction with the headmounted device. Theaudio rendering system may comprise one or more speakers 234-1 through234-6 to render sounds accompanying the rendering/displaying of theperipheral-vision expanded images. The audio rendering system mayimplement corresponding audio source position adaptation operations torender the sound sources according to the viewer's position and viewdirection as well as matching the new (or retargeted) sound sourcepositions that correspond to retargeted objects and/or image details asrepresented in the peripheral-vision expanded images. As a result, theperipheral-vision expanded images present to the viewer by way of theviewer's headmounted device (230) and the audio rendering system with arelatively large (or enhanced) field of view, immersive stereo ormulti-view images, a (virtual or real) screen of curvature,realistic/immersive audio.

FIG. 2D illustrates an example peripheral-vision expanded image 200. Theperipheral-vision expanded image (200) comprises multiple image portionsthat are adapted from multiple corresponding image portions in acorresponding source image. Instead of directly encoding the sourceimage, the peripheral-vision expanded image (200) is encoded into avideo signal that can be transmitted from one or more upstream devices(e.g., video streaming server(s), etc.) to a downstream recipient device(e.g., a video streaming client, etc.).

An image portion in an image as described herein may logically representan image frame containing a set of pixel values at a set of pixels (orpositions). Individual shapes (e.g., rectangle, polygonal shapes,regular shapes, irregular shapes, etc.) and individual sizes of imageportions and/or corresponding buffers used to store the image portionsmay be reshaped or resized dynamically, for example, based on one ormore of: network latencies, bandwidths, view direction movements, imagecontent, etc. At the one or more upstream devices and/or at therecipient device, each image portion (or each image frame) in theperipheral-vision expanded (200) may, but is not limited to only, bekept in a respective memory buffer in a plurality of memory buffers thatstores the peripheral-vision expanded image (200).

In some embodiments, some or all of the memory buffers may be refreshedcollectively with a common frame rate. In some embodiments, at leastsome of the memory buffers may be refreshed individually with their ownframe rates. In some embodiments, image data in different memory buffersas described herein may be compressed collectively, individually orseparately. In some embodiments, different memory buffers storingdifferent image layers may be located in different computing devices ofone or more content delivery networks, one or more content distributionnetworks, one or more core networks, one or more access networks, etc.

For example, a memory buffer storing a focal-vision image portion of aperipheral-vision expanded image may be kept relatively close (e.g.,geographically, in network topology, in the same network, in the sameservice-provider network, in an access network, via a local WIFI orwireline network/data connection, over relatively few network hops,etc.) to the recipient device. Another memory buffer storing anon-focal-vision image portion of the peripheral-vision expanded imagemay be kept relatively further way (e.g., geographically, in networktopology, in different networks, in different service-provider networks,in a core network, via one or more remote network/data connections, overrelatively numerous network hops, etc.) from the recipient device.

The peripheral-vision expanded image (200) may comprise a focal-visionimage portion 202 that covers a focal-vision region of the viewer'svision field. In some embodiments, the focal-vision image portion (202)covers a focal-vision region (e.g., completely, substantially within a +or −5% safety margin, etc.) that corresponds to an innermost portion(e.g., 50%, 70%, 90%, etc.) of the viewer's foveal-vision. In someembodiments, the foveal-vision image portion (202) covers a focal-visionregion (e.g., completely, substantially within a + or −5% safety margin,etc.) that corresponds to the viewer's foveal-vision and some or all ofthe viewer's near-peripheral vision.

Image data in the focal-vision image portion (202) may be cached andserved out at a relatively high data rate to the downstream recipientdevice at upstream devices, content serving nodes, content cachingnodes, etc., that are relatively close in spatial proximity or networktopology proximity to the downstream recipient device. The focal-visionimage portion (202) may be of no distortion or the least distortion incomparison with a corresponding image portion (of the source image) fromwhich the focal-vision image portion (202) is derived. Additionally,optionally or alternatively, the focal-vision image portion (202)comprise pixel values of depth data portions of the highest accuracy andfidelity and the least spatial distortion, the highest dynamic range,the widest color gamut, the highest spatial resolution, etc., astransmitted in a video signal from one or more upstream devices (e.g.,cloud-based video streaming server(s), a set-top box, a local videostreaming server, any combination of one or more of the foregoing,etc.).

The peripheral-vision expanded image (200) may comprise aperipheral-vision image portion 204 that cover a peripheral-visionregion in the viewer's vision field outside the focal-vision region.Image data in the peripheral-vision image portion (204) may be cachedand served out at a relatively low data rate to the downstream recipientdevice at upstream devices, content serving nodes, content cachingnodes, etc., that are relatively far in spatial proximity or networktopology proximity to the downstream recipient device. Theperipheral-vision image portion (204) may be of (e.g., spatiallyvarying, from the least to the most significant, etc.) distortions incomparison with a corresponding image portion (of the source image) fromwhich the peripheral-vision image portion (204) is derived.Additionally, optionally or alternatively, the peripheral-vision imageportion (204) may comprise pixel values of depth data portions ofrelatively low accuracy and fidelity and relatively significant spatialdistortion, relatively low dynamic range(s), relatively narrow colorgamut(s), relatively low spatial resolution(s), etc., as transmitted inthe video signal from one or more upstream devices (e.g., cloud-basedvideo streaming server(s), a set-top box, a local video streamingserver, any combination of one or more of the foregoing, etc.).

In some embodiments, the focal-vision image portion (202) and theperipheral-vision image portion (204) may cover the viewer's viewport206 as supported by the viewer's headmounted device (e.g., 230 of FIG.2A and FIG. 2B, etc.) in reference to the viewer's view directiondetermined or predicted for the time point.

As used herein, a viewport may refer to a total display area (or a totalimage rendering surface) available from one or more image displays (orone or more target displays) of a viewer on which a display imagegenerated from the peripheral-vision expanded image (200) is rendered.The peripheral-vision expanded image (200) in reference to the viewer'sview direction determined or predicted for the time point may cover animage field (e.g., immersive, panorama, 360-degree view, much, etc.)larger than the viewer's viewport (206).

The peripheral-vision expanded image (200) may be used to cover theentirety of the viewport plus a safety margin. If the peripheral-visionexpanded image (200) happens to be insufficient to cover the entirety ofthe viewport, then filler pixels may be used for some (e.g., tiny, etc.)portions inside the viewport.

In some embodiments, multiple focal-vision image portions may begenerated in the peripheral-vision expanded image (200) generated inreference to the viewer's view direction determined or predicted for atime point at which the peripheral-vision expanded image (200) is to berendered. Additionally, optionally or alternatively, multipleperipheral-vision (e.g., near-peripheral, mid-peripheral,far-peripheral, etc.) image portions may be generated in theperipheral-vision expanded image (200) generated in reference to theviewer's view direction determined or estimated for a time point atwhich the peripheral-vision expanded image (200) is to be rendered.

In some embodiments, one or more other image portions in addition tofocal-vision and peripheral-vision image portions may be generated for aperipheral-vision expanded image as described herein. The other imageportions and the focal-vision and peripheral-vision image portionscollectively represent all the image data in the peripheral-visionexpanded image generated in reference to the viewer's view directiondetermined or predicted for a time point at which a display mapped imagegenerated from the peripheral-vision expanded image (200) is to berendered.

Image metadata (e.g., peripheral-vision expansion metadata, displaymanagement metadata, etc.) that indicates how an image, and imageportions therein, should be spatially distorted may be generated by avideo streaming server for peripheral-vision expanded video content.Under techniques as described herein,

Based on the image metadata, a recipient device can apply differentspatial distortions (including but not limited to no distortion for afocal-vision image portion) in different image portions of an image thatis received or decoded, along with the image metadata, in a videosignal.

5. Example Video Streaming Servers and Clients

Techniques as described herein can be implemented to benefit consumersor viewers of various types of video-related applications (including butnot limited to VR applications) by providing them with a premiumexperience the same as or similar to a cinema-immersive viewingexperience when watching display or rendered images sourced from varioustypes of video content (including but to limited to traditional contentdesignated or optimized to be viewed with a limited viewport of atraditional image display, etc.).

FIG. 3A illustrates an example video streaming server 300 that comprisesa peripheral-vision-expanded image processor 302, aperipheral-vision-expanded image generator 312, etc.

Content producers or distributors can use the method to generatecinema-immersive content in a video application such as a VRapplication, an AR application, a remote presence application, acomputer gaming application, a home video display application, etc., forexample with a headmounted device operated by a viewer. In someembodiments, the peripheral-vision-expanded image processor (302)comprises a source image receiver 306, a data repository 310, etc. Someor all of the components of the video streaming server (300) may beimplemented by one or more devices, modules, units, etc., in software,hardware, a combination of software and hardware, etc.

In some embodiments, the source image receiver (306) comprises software,hardware, a combination of software and hardware, etc., configured toreceive an input source image stream 304 from a source image source suchas a local data store, a cloud-based source image source, a camerasystem in connection with a VR application, an AR application, a remotepresence application, a display application, etc.; decode the inputsource image stream (304) into one or more input source images (e.g., atime sequence of input 2D or 3D source images, etc.); etc.

Example input source images may include, but are not necessarily limitedto only, traditional content designated to be presented in a viewport ofless than 30 degrees, 50 degrees, 70 degrees, etc. By comparison,peripheral-vision expanded images generated from the source images maysupport an expanded viewport (e.g., of a VR headmounted device, an ARheadmounted device, etc.) that is 50%, 100%, etc., more than theviewport typically associated with presenting the traditional content ina rectangular display. The peripheral-vision expanded images may cover aviewport of no less than 180 degrees, and/or up to 360 degrees.

In some embodiments, the data repository (310) represents one or moredatabases, one or more data storage units/modules/devices, etc.,configured to support operations such as storing, updating, retrieving,deleting, etc., with respect to some or all of the input source images,etc.

In some embodiments, the peripheral-vision-expanded image generator(308) comprises software, hardware, a combination of software andhardware, etc., configured to receive, via a bidirectional data flow314, a viewer's view direction data; establish/determine the viewer'sview directions (e.g., for each of the two eyes, etc.) over time inrelation to a spatial coordinate system in which peripheral-visionexpanded video content, or a derivative version thereof, is to berendered in the viewer's image rendering device (or display device);generate an overall video stream encoded with the peripheral-visionexpanded video content and/or corresponding image metadata, etc. Theperipheral-vision expanded video content and/or corresponding imagemetadata may be separately and specifically generated in reference tothe viewer's (e.g., determined, predicted, estimated, etc.) viewdirections at respective time points, and may be delivered to adownstream device via the bidirectional data flow 314 (e.g., directly orindirectly through intermediate devices, etc.). The downstream devicemay represent a video streaming client, a display device, a storagedevice, a video decoder operating with a target display, etc.

Additionally, optionally, or alternatively, some or all of imageprocessing operations such as image rotation determination, imagealignment analysis, scene cut detections, transformation betweencoordinate systems, temporal dampening, display management, contentmapping, color mapping, field-of-view management, etc., may be performedby the video streaming server (300).

The video streaming server (300) may be used to support real timeimmersive video applications, near-real-time immersive videoapplications, real time non-immersive video applications, near-real-timenon-immersive video applications, non-real-time immersive videoapplications, virtual reality, augmented reality, automobileentertainment, helmet mounted display applications, heads up displayapplications, games, 2D display applications, 3D display applications,multi-view display applications, etc. For example, some or all of viewdirection tracking data, peripheral-vision expanded video content and/orcorresponding image metadata generated in reference to the viewer's viewdirections, etc., are generated or accessed by the video streamingserver (300) in real time, in near real time, etc.

FIG. 3B illustrates an example image rendering system 324-1 thatcomprises a peripheral-vision-expanded image receiver 316, a viewdirection tracker 326, a display manager 318, one or more image displays(or one or more target displays) 320, etc. Some or all of the componentsof the image rendering system (324-1) may be implemented by one or moredevices, modules, units, etc., in software, hardware, a combination ofsoftware and hardware, etc.

In some embodiments, the peripheral-vision-expanded image receiver (316)comprises software, hardware, a combination of software and hardware,etc., configured to send, via a bidirectional data flow 314, theviewer's view direction tracking data, which can be used by a videostreaming server to establish/determine the viewer's view directionsover time in relation to a spatial coordinate system in whichperipheral-vision expanded video content is to be rendered in theviewer's image displays (320); receive an overall video stream encodedwith the peripheral-vision expanded video content and/or the imagemetadata derived from the source images; etc.

The user may move the user's view directions at runtime. In someembodiments, the view direction tracker (326) comprises software,hardware, a combination of software and hardware, etc., configured togenerate view direction data related to the viewer over time. The viewdirection tracking data may be sampled or measured at a relatively finetime scale (e.g., every millisecond, every five milliseconds, etc.). Theview direction tracking data may be used to establish/determine theviewer's view directions at a given time resolution (e.g., everymillisecond, every five milliseconds, etc.).

In some embodiments, the image rendering system (324-1) is configured togenerate display video content, based on the peripheral-vision expandedvideo content and/or the image metadata, to be rendered on the user'sdisplay. De-blocking operations, de-contouring operations, blurringoperations, directional and/or non-directional filtering, etc., may beperformed as a part of compositing the unified imagery to be rendered onthe user's display.

In some embodiments, the display manager (318) comprises software,hardware, a combination of software and hardware, etc., configured toperform image processing operations (including but not limited to DMoperations) on the peripheral-vision expanded video content to generatethe display video content; output the display video content (e.g., in anHDMI signal, etc.) to the image displays (320) for rendering; etc.

Additionally, optionally, or alternatively, some or all of imagerendering operations such as view direction tracking, motion detection,position detection, rotation determination, transformation betweencoordinate systems, temporal dampening of time-varying image parameters,any other temporal manipulation of image parameters, display management,content mapping, tone mapping, color mapping, field-of-view management,prediction, navigations through mouse, trackball, keyboard, foottracker, actual body motion, etc., may be performed by the imagerendering system (324-1).

The image rendering system (324-1) may be used to support real timeimmersive video applications, near-real-time immersive videoapplications, non-real-time immersive video applications, real timenon-immersive video applications, near-real-time non-immersive videoapplications, non-real-time non-immersive video applications, virtualreality, augmented reality, automobile entertainment, helmet mounteddisplay applications, heads up display applications, games, 2D displayapplications, 3D display applications, multi-view display applications,etc. For example, some or all of view direction data, multiple imageportions and multiple DM metadata portions generated in reference to theviewer's view directions, etc., are generated or accessed by the imagerendering system (324-1) in real time, in near real time, etc.

Techniques as described herein can be implemented in a variety of systemarchitectures. Some or all image processing operations as describedherein can be implemented by one or more of cloud-based video streamingservers, video streaming servers collocated with or incorporated intovideo streaming clients, image rendering systems, image renderingsystems, display devices, etc. Based on one or more factors such astypes of video applications, bandwidth/bitrate budgets, computingcapabilities, resources, loads, etc., of recipient devices, computingcapabilities, resources, loads, etc., of video streaming servers and/orcomputer networks, etc., some image processing operations can beperformed by a video streaming server, while some other image processingoperations can be performed by a video streaming client, an imagerendering system, a display device, etc.

FIG. 3C illustrates an example configuration in which aperipheral-vision-expanded image generator (e.g., 312, etc.) isincorporated into an edge video streaming server 324-2. In someembodiments, a peripheral-vision-expanded image processor 302 of FIG. 3Cmay be cloud-based. In some embodiments, the peripheral-vision-expandedimage processor (302) may be located in a core network separate fromedge devices such as the edge video streaming server (324-2). As in FIG.3A, the peripheral-vision-expanded image processor (302) may comprise asource image receiver 306, a data repository 310, etc. Theperipheral-vision-expanded image processor (302) may represent anupstream video streaming server that communicates with the edge videostreaming server (324-2) over relatively high bitrates. Some or all ofthe components of the peripheral-vision-expanded image processor (302)and/or the edge video streaming server (324-2) may be implemented by oneor more devices, modules, units, etc., in software, hardware, acombination of software and hardware, etc.

In some embodiments, the peripheral-vision-expanded image processor(302) is configured to output source images in a data flow 322 todownstream devices one of which may be the edge video streaming server(324-2).

In some embodiments, the edge video streaming server (324-2), or theperipheral-vision-expanded image generator (312) therein, comprisessoftware, hardware, a combination of software and hardware, etc.,configured to determine a viewer's view direction over time in relationto a spatial coordinate system in which peripheral-vision expanded videocontent is to be rendered in the viewer's display device; generate anoverall video stream encoded with the peripheral-vision expanded videocontent and/or corresponding image metadata derived from the sourceimages, etc. The peripheral-vision expanded video content and/orcorresponding image metadata may be separately and specificallygenerated in reference to the viewer's (e.g., determined, predicted,estimated, etc.) view directions at respective time points, and may bedelivered to a downstream device via the bidirectional data flow 314(e.g., directly or indirectly through intermediate devices, etc.).

In some embodiments, an image rendering device (e.g., 324-1), or adisplay manager (e.g., 318 of FIG. 3B) therein, comprises software,hardware, a combination of software and hardware, etc., configured toperform image processing operations on the peripheral-vision expandedvideo content to generate display video content; output the displayvideo content (e.g., in an HDMI signal, etc.) to the image displays forrendering; etc.

The viewer may move the viewer's view directions at runtime. The imagerendering system (324-2) is configured to generate peripheral-visionexpanded video content (or a derivative version thereof) to be renderedon the viewer's display device. De-blocking operations, de-contouringoperations, blurring operations, etc., may be performed as a part ofcompositing the unified imagery to be rendered on the user's display.

6. Example Process Flows

FIG. 4A illustrates an example process flow according to an exampleembodiment. In some example embodiments, one or more computing devicesor components may perform this process flow. In block 402, aperipheral-vision-expanded image processor (e.g., a video streamingserver or a video streaming client of FIG. 3A through FIG. 3C, etc.)streams to a video streaming client, one or more peripheral-visionexpanded images. The one or more peripheral-vision expanded images areto be used by the video streaming client to generate one or more displayimages for rendering to a viewer at one or more time points. The one ormore peripheral-vision expanded images are generated from one or moresource images in reference to one or more view directions of the viewerat the one or more time points.

In block 404, the peripheral-vision-expanded image processor receives atleast a part of view direction data of the viewer collected in real timewhile the viewer is viewing the one or more display images. The viewdirection data is used to determine a second view direction of theviewer at a second time point subsequent to the one or more time points;

In block 406, the peripheral-vision-expanded image processor generates asecond peripheral-vision expanded image from a second source image inreference to the second view direction of the viewer at the second timepoint. The second peripheral-vision expanded image is to be used by thevideo streaming client to generate a second display image for renderingto the viewer at the second time point. The second peripheral-visionexpanded image has a focal-vision image portion covering the second viewdirection of the viewer and a peripheral-vision image portion outsidethe focal-vision image portion. The focal-vision image portion of thesecond peripheral-vision expanded image is generated from a firstcorresponding source image portion in the second source image to coverthe viewer's focal vision as covered by the first corresponding sourceimage portion. The peripheral-vision image portion of the secondperipheral-vision expanded image is generated by spatially stretching asecond corresponding source image portion in the second source image tocover the viewer's peripheral vision including one or more peripheralvision portions not covered by the second corresponding source imageportion of the second source image.

In block 408, the peripheral-vision-expanded image processor transmitsthe second peripheral-vision expanded image to the video streamingclient.

In an embodiment, the peripheral-vision-expanded image processor isfurther configured to perform: generating image metadata to betransmitted to the video streaming client; the image metadata is used bythe video streaming client to generate peripheral-vision expanded videocontent.

In an embodiment, the second peripheral-vision expanded image representsone of: an immersive image, a panorama image, an augmented realityimage, a virtual reality image, a remote presence image, etc.

In an embodiment, the one or more time points and the second time pointcollectively represent consecutive time points covering a time interval.

In an embodiment, the second focal-vision image portion in the seconddisplay image covers the viewer's foveal-vision up to a maximum linearangular value: between 2 and 4 degrees, between 4 and 6 degrees, between6 and 8 degrees, and so forth.

In an embodiment, the one or more source images and the second sourceimage are a part of two-dimensional (2D) video content designated to bepresented on a rectangular image rendering surface with a relativelylimited field of view.

In an embodiment, the one or more display images and the second displayimage are a part of peripheral-vision expanded video content designatedto be presented on a target display of headmounted device of the viewerwith a relatively large field of view.

In an embodiment, the one or more display images and the second displayimage are a part of peripheral-vision expanded video content designatedto be presented on a target display of headmounted device of the viewerwith a relatively large field of view.

In an embodiment, a sound source as visually depicted in the one or moredisplay images and the second display image is moved from an originalspatial position in the one or more source images and the second sourceimage to a new spatial position in the one or more display images andthe second display image; the peripheral-vision-expanded image processoris further configured to perform: causing an audio rendering system torender sounds designated to be emitted from the sound source from thenew spatial position.

In an embodiment, the one or more display images and the second displayimage is rendered with a curved screen; and wherein the curved screen isa virtual display screen.

In an embodiment, the one or more display images and the second displayimage comprise three-dimensional (3D) display image portions.

In an embodiment, the one or more source images and the second sourceimage represent two-dimensional (2D) images; the 3D display imageportions are generated using depth data portions generated from applying2D to 3D conversion operations on corresponding 2D source image portionsin the one or more source images and the second source image.

In an embodiment, the depth data portions are used to determine whetherspecific objects in a peripheral region of the one or more source imageand the second source image are located relatively far away as comparedwith foveal vision objects; the peripheral-vision-expanded imageprocessor is further configured to perform: in response to determiningthat the specific objects in the peripheral region are locatedrelatively far away as compared with the foveal vision objects,increasing deterioration in one or more of: acuity, luminance dynamicrange, color precision, or bit depth, in the peripheral region of theone or more display images and the second display image.

In an embodiment, the 2D to 3D conversion operations are dependent on anindividual inter-pupil distance of the viewer.

In an embodiment, the 2D to 3D conversion operations are performed bypositioning two virtual cameras in the viewer's eyes with an individualinter-pupil distance of the viewer.

In an embodiment, one or more depicted objects in the peripheral-visionimage portion of the second peripheral-vision expanded image areseamlessly stretched as compared with one or more corresponding depictedobjects in the second corresponding image portion of the second sourceimage.

In an embodiment, the one or more depicted objects are seamlesslystretched through one or more of: warping operations, reverse fisheyemapping, linear stretching along a spatial direction, projectionoperations, conformal mapping, projections analogous to those used inconnection with architecture drawings, panini projections, or otherprojection operations.

In an embodiment, the peripheral-vision image portion of the secondperipheral-vision expanded image is of a relatively low resolution ascompared with the focal-vision image portion of the secondperipheral-vision expanded image.

FIG. 4B illustrates an example process flow according to an exampleembodiment. In some example embodiments, one or more computing devicesor components may perform this process flow. In block 452, a videostreaming client (e.g., an image rendering system of FIG. 3B, etc.)renders, to a viewer, one or more display images at one or more timepoints, the one or more display images being generated from one or moreperipheral-vision expanded images received from a video streamingserver. The one or more peripheral-vision expanded images are generatedby the video streaming server from one or more source images inreference to one or more view directions of the viewer at the one ormore time points.

In block 454, the video streaming client collects, in real time, viewdirection data of the viewer collected while the viewer is viewing theone or more display images, the view direction data being used todetermine a second view direction of the viewer at a second time pointsubsequent to the one or more time points.

In block 456, the video streaming client sends at least a part of theview direction data to the video streaming server to cause the videostreaming server to generate a second peripheral-vision expanded imagefrom a second source image in reference to the second view direction ofthe viewer at the second time point, the second peripheral-visionexpanded image to be used to generate a second display image forrendering to the viewer at the second time point, the secondperipheral-vision expanded image having a focal-vision image portioncovering the second view direction of the viewer and a peripheral-visionimage portion outside the focal-vision image portion, the focal-visionimage portion of the second peripheral-vision expanded image beinggenerated from a first corresponding source image portion in the secondsource image to cover the viewer's focal vision as covered by the firstcorresponding source image portion, the peripheral-vision image portionof the second peripheral-vision expanded image being generated byspatially stretching a second corresponding source image portion in thesecond source image to cover the viewer's peripheral vision includingone or more peripheral vision portions not covered by the secondcorresponding source image portion of the second source image.

In block 458, the video streaming client receives the secondperipheral-vision expanded image from the video streaming server.

In block 460, the video streaming client generates the second displayimage from the second peripheral-vision expanded image.

In block 462, the video streaming client renders at the second timepoint, to the viewer, the second display image.

In an embodiment, the one or more display images and the second displayimage are rendered on a target display on a headmounted device of theviewer.

In various example embodiments, an apparatus, a system, an apparatus, orone or more other computing devices performs any or a part of theforegoing methods as described. In an embodiment, a non-transitorycomputer readable storage medium stores software instructions, whichwhen executed by one or more processors cause performance of a method asdescribed herein.

Note that, although separate embodiments are discussed herein, anycombination of embodiments and/or partial embodiments discussed hereinmay be combined to form further embodiments.

7. Implementation Mechanisms—Hardware Overview

According to one embodiment, the techniques described herein areimplemented by one or more special-purpose computing devices. Thespecial-purpose computing devices may be hard-wired to perform thetechniques, or may include digital electronic devices such as one ormore application-specific integrated circuits (ASICs) or fieldprogrammable gate arrays (FPGAs) that are persistently programmed toperform the techniques, or may include one or more general purposehardware processors programmed to perform the techniques pursuant toprogram instructions in firmware, memory, other storage, or acombination. Such special-purpose computing devices may also combinecustom hard-wired logic, ASICs, or FPGAs with custom programming toaccomplish the techniques. The special-purpose computing devices may bedesktop computer systems, portable computer systems, handheld devices,networking devices or any other device that incorporates hard-wiredand/or program logic to implement the techniques.

For example, FIG. 5 is a block diagram that illustrates a computersystem 500 upon which an example embodiment may be implemented. Computersystem 500 includes a bus 502 or other communication mechanism forcommunicating information, and a hardware processor 504 coupled with bus502 for processing information. Hardware processor 504 may be, forexample, a general purpose microprocessor.

Computer system 500 also includes a main memory 506, such as a randomaccess memory (RAM) or other dynamic storage device, coupled to bus 502for storing information and instructions to be executed by processor504. Main memory 506 also may be used for storing temporary variables orother intermediate information during execution of instructions to beexecuted by processor 504. Such instructions, when stored innon-transitory storage media accessible to processor 504, rendercomputer system 500 into a special-purpose machine that is customized toperform the operations specified in the instructions.

Computer system 500 further includes a read only memory (ROM) 508 orother static storage device coupled to bus 502 for storing staticinformation and instructions for processor 504.

A storage device 510, such as a magnetic disk or optical disk, solidstate RAM, is provided and coupled to bus 502 for storing informationand instructions.

Computer system 500 may be coupled via bus 502 to a display 512, such asa liquid crystal display, for displaying information to a computer user.An input device 514, including alphanumeric and other keys, is coupledto bus 502 for communicating information and command selections toprocessor 504. Another type of user input device is cursor control 516,such as a mouse, a trackball, or cursor direction keys for communicatingdirection information and command selections to processor 504 and forcontrolling cursor movement on display 512. This input device typicallyhas two degrees of freedom in two axes, a first axis (e.g., x) and asecond axis (e.g., y), that allows the device to specify positions in aplane.

Computer system 500 may implement the techniques described herein usingcustomized hard-wired logic, one or more ASICs or FPGAs, firmware and/orprogram logic which in combination with the computer system causes orprograms computer system 500 to be a special-purpose machine. Accordingto one embodiment, the techniques herein are performed by computersystem 500 in response to processor 504 executing one or more sequencesof one or more instructions contained in main memory 506. Suchinstructions may be read into main memory 506 from another storagemedium, such as storage device 510. Execution of the sequences ofinstructions contained in main memory 506 causes processor 504 toperform the process steps described herein. In some embodiments,hard-wired circuitry may be used in place of or in combination withsoftware instructions.

The term “storage media” as used herein refers to any non-transitorymedia that store data and/or instructions that cause a machine tooperation in a specific fashion. Such storage media may comprisenon-volatile media and/or volatile media. Non-volatile media includes,for example, optical or magnetic disks, such as storage device 510.Volatile media includes dynamic memory, such as main memory 506. Commonforms of storage media include, for example, a floppy disk, a flexibledisk, hard disk, solid state drive, magnetic tape, or any other magneticdata storage medium, a CD-ROM, any other optical data storage medium,any physical medium with patterns of holes, a RAM, a PROM, and EPROM, aFLASH-EPROM, NVRAM, any other memory chip or cartridge.

Storage media is distinct from but may be used in conjunction withtransmission media. Transmission media participates in transferringinformation between storage media. For example, transmission mediaincludes coaxial cables, copper wire and fiber optics, including thewires that comprise bus 502. Transmission media can also take the formof acoustic or light waves, such as those generated during radio-waveand infra-red data communications.

Various forms of media may be involved in carrying one or more sequencesof one or more instructions to processor 504 for execution. For example,the instructions may initially be carried on a magnetic disk or solidstate drive of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 500 canreceive the data on the telephone line and use an infra-red transmitterto convert the data to an infra-red signal. An infra-red detector canreceive the data carried in the infra-red signal and appropriatecircuitry can place the data on bus 502. Bus 502 carries the data tomain memory 506, from which processor 504 retrieves and executes theinstructions. The instructions received by main memory 506 mayoptionally be stored on storage device 510 either before or afterexecution by processor 504.

Computer system 500 also includes a communication interface 518 coupledto bus 502. Communication interface 518 provides a two-way datacommunication coupling to a network link 520 that is connected to alocal network 522. For example, communication interface 518 may be anintegrated services digital network (ISDN) card, cable modem, satellitemodem, or a modem to provide a data communication connection to acorresponding type of telephone line. As another example, communicationinterface 518 may be a local area network (LAN) card to provide a datacommunication connection to a compatible LAN. Wireless links may also beimplemented. In any such implementation, communication interface 518sends and receives electrical, electromagnetic or optical signals thatcarry digital data streams representing various types of information.

Network link 520 typically provides data communication through one ormore networks to other data devices. For example, network link 520 mayprovide a connection through local network 522 to a host computer 524 orto data equipment operated by an Internet Service Provider (ISP) 526.ISP 526 in turn provides data communication services through the worldwide packet data communication network now commonly referred to as the“Internet” 528. Local network 522 and Internet 528 both use electrical,electromagnetic or optical signals that carry digital data streams. Thesignals through the various networks and the signals on network link 520and through communication interface 518, which carry the digital data toand from computer system 500, are example forms of transmission media.

Computer system 500 can send messages and receive data, includingprogram code, through the network(s), network link 520 and communicationinterface 518. In the Internet example, a server 530 might transmit arequested code for an application program through Internet 528, ISP 526,local network 522 and communication interface 518.

The received code may be executed by processor 504 as it is received,and/or stored in storage device 510, or other non-volatile storage forlater execution.

8. Equivalents, Extensions, Alternatives and Miscellaneous

In the foregoing specification, example embodiments of the inventionhave been described with reference to numerous specific details that mayvary from implementation to implementation. Thus, the sole and exclusiveindicator of what is the invention, and is intended by the applicants tobe the invention, is the set of claims that issue from this application,in the specific form in which such claims issue, including anysubsequent correction. Any definitions expressly set forth herein forterms contained in such claims shall govern the meaning of such terms asused in the claims. Hence, no limitation, element, property, feature,advantage or attribute that is not expressly recited in a claim shouldlimit the scope of such claim in any way. The specification and drawingsare, accordingly, to be regarded in an illustrative rather than arestrictive sense.

What is claimed is:
 1. A method for providing image data to support immersive media content consumption experiences, comprising: streaming to a video streaming client, one or more peripheral-vision expanded images, the one or more peripheral-vision expanded images to be used by the video streaming client to generate one or more display images for rendering to a viewer at one or more time points, the one or more peripheral-vision expanded images being generated from one or more source images in reference to one or more view directions of the viewer at the one or more time points; receiving at least a part of view direction data of the viewer collected in real time while the viewer is viewing the one or more display images, the view direction data being used to determine a second view direction of the viewer at a second time point subsequent to the one or more time points; generating a second peripheral-vision expanded image from a second source image in reference to the second view direction of the viewer at the second time point, the second peripheral-vision expanded image to be used by the video streaming client to generate a second display image for rendering to the viewer at the second time point, the second peripheral-vision expanded image having a focal-vision image portion covering the second view direction of the viewer and a peripheral-vision image portion outside the focal-vision image portion, the focal-vision image portion of the second peripheral-vision expanded image being generated from a first corresponding source image portion in the second source image to cover the viewer's focal vision as covered by the first corresponding source image portion, the peripheral-vision image portion of the second peripheral-vision expanded image being generated by spatially stretching a second corresponding source image portion in the second source image to cover the viewer's peripheral vision including one or more peripheral vision portions not covered by the second corresponding source image portion of the second source image; transmitting the second peripheral-vision expanded image to the video streaming client.
 2. The method of claim 1, further comprising: generating image metadata to be transmitted to the video streaming client, wherein the image metadata is used by the video streaming client to generate peripheral-vision expanded video content.
 3. The method of claim 1, wherein the second peripheral-vision expanded image represents one of: an immersive image, a panorama image, an augmented reality image, a virtual reality image, or a remote presence image.
 4. The method of claim 1, wherein the one or more time points and the second time point collectively represent consecutive time points covering a time interval.
 5. The method of claim 1, wherein the second focal-vision image portion in the second display image covers the viewer's foveal-vision up to a maximum linear angular value: between 2 and 4 degrees, between 4 and 6 degrees, between 6 and 8 degrees, or another angular value range.
 6. The method of claim 1, wherein the one or more source images and the second source image are a part of two-dimensional (2D) video content designated to be presented on a rectangular image rendering surface with a relatively limited field of view.
 7. The method of claim 1, wherein the one or more display images and the second display image are a part of peripheral-vision expanded video content designated to be presented on a target display of headmounted device of the viewer with a relatively large field of view.
 8. The method of claim 1, wherein the one or more display images and the second display image are a part of peripheral-vision expanded video content designated to be presented on a target display of headmounted device of the viewer with a relatively large field of view.
 9. The method of claim 1, wherein a sound source as visually depicted in the one or more display images and the second display image is moved from an original spatial position in the one or more source images and the second source image to a new spatial position in the one or more display images and the second display image; the method further comprising: causing an audio rendering system to render sounds designated to be emitted from the sound source from the new spatial position.
 10. The method of claim 1, wherein the one or more display images and the second display image is rendered with a curved screen; and wherein the curved screen is a virtual display screen.
 11. The method of claim 1, wherein the one or more display images and the second display image comprise three-dimensional (3D) display image portions.
 12. The method of claim 11, wherein the one or more source images and the second source image represent two-dimensional (2D) images; and wherein the 3D display image portions are generated using depth data portions generated from applying 2D to 3D conversion operations on corresponding 2D source image portions in the one or more source images and the second source image.
 13. The method of claim 1, wherein one or more depicted objects in the peripheral-vision image portion of the second peripheral-vision expanded image are seamlessly stretched as compared with one or more corresponding depicted objects in the second corresponding image portion of the second source image.
 14. The method of claim 1, wherein the peripheral-vision image portion of the second peripheral-vision expanded image is of a relatively low resolution as compared with the focal-vision image portion of the second peripheral-vision expanded image.
 15. A method for providing immersive media content consumption experiences, comprising: rendering, to a viewer, one or more display images at one or more time points, the one or more display images being generated from one or more peripheral-vision expanded images received from a video streaming server, the one or more peripheral-vision expanded images being generated by the video streaming server from one or more source images in reference to one or more view directions of the viewer at the one or more time points; collecting, in real time, view direction data of the viewer collected while the viewer is viewing the one or more display images, the view direction data being used to determine a second view direction of the viewer at a second time point subsequent to the one or more time points; sending at least a part of the view direction data to the video streaming server to cause the video streaming server to generate a second peripheral-vision expanded image from a second source image in reference to the second view direction of the viewer at the second time point, the second peripheral-vision expanded image to be used to generate a second display image for rendering to the viewer at the second time point, the second peripheral-vision expanded image having a focal-vision image portion covering the second view direction of the viewer and a peripheral-vision image portion outside the focal-vision image portion, the focal-vision image portion of the second peripheral-vision expanded image being generated from a first corresponding source image portion in the second source image to cover the viewer's focal vision as covered by the first corresponding source image portion, the peripheral-vision image portion of the second peripheral-vision expanded image being generated by spatially stretching a second corresponding source image portion in the second source image to cover the viewer's peripheral vision including one or more peripheral vision portions not covered by the second corresponding source image portion of the second source image; receiving the second peripheral-vision expanded image from the video streaming server; generating the second display image from the second peripheral-vision expanded image; rendering at the second time point, to the viewer, the second display image.
 16. The method of claim 15, wherein the one or more display images and the second display image are rendered on a target display on a headmounted device of the viewer.
 17. An apparatus performing the method of claim
 1. 18. A system performing the method of claim
 1. 19. A non-transitory computer readable storage medium, storing software instructions, which when executed by one or more processors cause performance of the method recited in claim
 1. 20. A computing device comprising one or more processors and one or more non-transitory computer-readable storage media, storing a set of instructions, which when executed by one or more processors cause performance of the method recited in method claim
 1. 